1. Field of the Invention
The present invention relates to a liquid jetting apparatus which jets liquid and a method for adjusting inclination of a head holder of the liquid jetting apparatus.
2. Description of the Related Art
Conventionally, as liquid jetting apparatuses which jet liquids from a plurality of nozzles, an ink jet printer which performs printing on a recording paper by jetting inks from a plurality of nozzles formed in an ink jet head has been known. In such an ink jet printer, the ink jet head is attached such that a nozzle alignment direction may be oriented in a predetermined direction (to be referred to as a reference direction below) in the printer.
For example, a conventional image recording apparatus carries out printing on a recording paper transported along an X-direction (to be referred to as a transport direction below) perpendicular to a predetermined Y-direction, by jetting ink from an ink jet head placed on a carriage (a head holder) moving reciprocatingly and being guided by a guide member extending in the Y-direction (to be referred to as a scanning direction below). In the conventional image recording apparatus, the ink jet head is attached to the carriage such that the nozzle alignment direction may be parallel to the transport direction which is the reference direction.
However, due to some errors and the like in attaching the ink jet head to the carriage, in some cases, the nozzle alignment direction may be inclined with respect to the transport direction in a plane parallel to the ink jet surface in which the plurality of nozzles are formed. In such manner, when the nozzle alignment direction is inclined with respect to the transport direction, for example, if the ink is jetted with the same jet timing as the nozzle alignment direction is not inclined, then each of the landing positions of the ink jetted from the plurality of nozzles forming a nozzle row may possibly deviate in the scanning direction of the carriage, and the print quality is lowered.
Therefore, in order to prevent lowering the print quality, there are methods for correcting the inclination of the carriage (the ink jet head) so as to eliminate the inclination between the nozzle alignment direction and the transport direction in the plane parallel to the ink jet surface in which the plurality of nozzles are formed.
In the conventional image recording apparatus, the carriage is guided along the scanning direction by first and second slide projections, which are provided on the carriage and slide on a slide surface provided on the guide member along the scanning direction. The first slide projection is fixed on the carriage, whereas the second slide projection is configured to be slidable with respect to the carriage by a posture adjustment means (an inclination adjustment mechanism). It is possible to adjust the inclination of the carriage with respect to the guide member by rotating the second slide projection by the posture adjustment means with the first slide projection as a rotation axis.
The posture adjustment means includes an adjustment block formed integrally with the second slide projection, a circular eccentric shaft which has an outer circumferential surface and which is in contact with a contact surface of the adjustment block by the outer circumferential surface by being fitted into the adjustment block, a circular dial plate formed integrally with the circular eccentric shaft, etc. Then, the dial plate is turned to rotate the circular eccentric shaft. By virtue of this configuration, it is possible to change the position of the outer circumferential surface of the circular eccentric shaft, so as to move the adjustment block in contact with the circular eccentric shaft integrally with the second slide projection.
However, in order to increase the number of dots formable at one time for high-speed printing, it is preferable to elongate the nozzle row. However, the longer the nozzle row is, the more the reduction becomes in print quality due to the inclination of the nozzle alignment direction with respect to the transport direction (the reference direction). If the nozzle row is considerably long, then even though the nozzle row is only a little inclined with respect to the transport direction, the landing positions of the ink jetted respectively from the nozzles on both ends of the nozzle row deviate greatly in the scanning direction, thereby greatly lowering the print quality. Hence, in order to possibly eliminate even a little inclination, it is necessary to make it possible to adjust the inclination of the carriage (the head holder) in a highly minute manner. In order to minutely adjust the inclination of the head holder by the posture adjustment means (the inclination adjustment mechanism) of the conventional image recording appartus, it is necessary to minutely form grooves in the dial plate, or reduce the eccentricity of the circular eccentric shaft (the displacement amount is small with respect to the rotation angle).
However, if the grooves formed in the dial plate are simply made minute, then because the intervals of the grooves become small in the circumferential direction, considering the workability, it is necessary to enlarge the diameter of the dial plate. As a result, the inclination adjustment mechanism becomes large in size. On the other hand, if the eccentricity of the circular eccentric shaft is reduced, then the adjustment block (the second slide projection) has a narrow movable range. Hence, if the inclination is comparatively large, then the adjustment becomes impossible, thereby lowering the yield ratio.